Heat stress has an enormous economic impact on the global dairy industry, but the mechanisms by which hyperthermia negatively affect systemic physiology and milk synthesis are not clear. Study ...objectives were to evaluate production parameters and metabolic variables in lactating dairy cows during short-term heat stress or pair-fed conditions coupled with bST administration. Twenty-two multiparous Holstein cows were subjected to 3 experimental periods: 1) thermoneutral conditions with ad libitum intake for 7 d (P1); 2) heat stress (HS) with ad libitum intake (n=10) or pair-fed (PF) in thermoneutral conditions (n=12) for 7 d (P2), and 3) 7 d of HS or PF in conditions as described in P2 with recombinant bovine somatotropin administered on d 1 (P3). All cows received an intravenous glucose tolerance test (GTT) on d 5 of each period. Heat stress conditions were cyclical and temperatures ranged from 29.4 to 38.9°C. Rectal temperatures and respiration rates increased during heat stress (38.6–40.4°C and 44–89 breaths/min, respectively). Heat stress reduced dry matter intake by 30% and by design PF cows had similar intake reductions (28%). During heat stress and pair-feeding, milk yield decreased by 27.6% (9.6kg) and 13.9% (4.8kg), respectively, indicating that reduced feed intake accounted for only 50% of the decreased milk production. Milk yield increased with recombinant bovine somatotropin in both HS (9.7%) and PF (16.1%) cows. Cows in both groups were in positive energy balance (3.95 Mcal/d) during P1 but entered negative energy balance during P2 and P3 (−5.65 Mcal/d). Heat stress and pair-feeding treatments decreased (9.3%) basal glucose concentrations. Heat stress conditions had no effect on basal NEFA levels during P2; however, PF cows (despite a similar calculated energy balance) had a 2-fold increase in basal NEFA concentrations. Both groups had increased plasma urea nitrogen levels during P2 and P3 compared with P1. Basal insulin levels increased (37%) during P2 and P3 in HS cows but did not differ between periods in PF cows. During P2 and compared with P1, PF cows had a decreased rate of glucose disposal, whereas HS cows had a similar disposal rate following the GTT. During P2 and compared with P1, PF cows had a reduced insulin response whereas HS cows had a similar insulin response to the GTT. In summary, reduced nutrient intake accounted for only 50% of heat stress-induced decreases in milk yield, and feed intake-independent shifts in postabsorptive glucose and lipid homeostasis may contribute to the additional reduction in milk yield.
Heat stress is detrimental to dairy production and affects numerous variables including feed intake and milk production. It is unclear, however, whether decreased milk yield is primarily due to the ...associated reduction in feed intake or the cumulative effects of heat stress on feed intake, metabolism, and physiology of dairy cattle. To distinguish between direct (not mediated by feed intake) and indirect (mediated by feed intake) effects of heat stress on physiological and metabolic indices, Holstein cows (n = 6) housed in thermal neutral conditions were pair-fed (PF) to match the nutrient intake of heat-stressed cows (HS; n = 6). All cows were subjected to 2 experimental periods: 1) thermal neutral and ad libitum intake for 9 d (P1) and 2) HS or PF for 9 d (P2). Heat-stress conditions were cyclical with daily temperatures ranging from 29.7 to 39.2°C. During P1 and P2 all cows received i.v. challenges of epinephrine (d 6 of each period), and growth hormone releasing factor (GRF; d 7 of each period), and had circulating somatotropin (ST) profiles characterized (every 15 min for 6 h on d 8 of each period). During P2, HS cows were hyperthermic for the entire day and peak differences in rectal temperatures and respiration rates occurred in the afternoon (38.7 to 40.2°C and 46 to 82 breaths/min, respectively). Heat stress decreased dry matter intake by greater than 35% and, by design, PF cows had similar reduced intakes. Heat stress and PF decreased milk yield, although the pattern and magnitude (40 and 21%, respectively) differed between treatments. The reduction in dry matter intake caused by HS accounted for only approximately 35% of the decrease in milk production. Both HS and PF cows entered into negative energy balance, but only PF cows had increased (approximately 120%) basal nonesterified fatty acid (NEFA) concentrations. Both PF and HS cows had decreased (7%) plasma glucose levels. The NEFA response to epinephrine did not differ between treatments but was increased (greater than 50%) in all cows during P2. During P2, HS (but not PF) cows had a modest reduction (16%) in plasma insulin-like growth factor-I. Neither treatment nor period had an effect on the ST response to GRF and there was little or no treatment effect on mean ST levels or pulsatility characteristics, but both HS and PF cows had reduced mean ST concentrations during P2. In summary, reduced nutrient intake accounted for just 35% of the HS-induced decrease in milk yield, and modest changes in the somatotropic axis may have contributed to a portion of the remainder. Differences in basal NEFA between PF and HS cows suggest a shift in postabsorptive metabolism and nutrient partitioning that may explain the additional reduction in milk yield in cows experiencing a thermal load.
ABSTRACT
We study the late-time evolution of the central regions of two Milky Way (MW)-like simulations of galaxies formed in a cosmological context, one hosting a fast bar and the other a slow one. ...We find that bar length, Rb, measurements fluctuate on a dynamical time-scale by up to 100 per cent, depending on the spiral structure strength and measurement threshold. The bar amplitude oscillates by about 15 per cent, correlating with Rb. The Tremaine–Weinberg method estimates of the bars’ instantaneous pattern speeds show variations around the mean of up to $\sim \!20{{\ \rm per\ cent}}$, typically anticorrelating with the bar length and strength. Through power spectrum analyses, we establish that these bar pulsations, with a period in the range ∼60–200 Myr, result from its interaction with multiple spiral modes, which are coupled with the bar. Because of the presence of odd spiral modes, the two bar halves typically do not connect at exactly the same time to a spiral arm, and their individual lengths can be significantly offset. We estimated that in about 50 per cent of bar measurements in MW-mass external galaxies, the bar lengths of SBab-type galaxies are overestimated by $\sim \!15{{\ \rm per\ cent}}$ and those of SBbc types by $\sim \!55{{\ \rm per\ cent}}$. Consequently, bars longer than their corotation radius reported in the literature, dubbed ‘ultrafast bars’, may simply correspond to the largest biases. Given that the Scutum–Centaurus arm is likely connected to the near half of the MW bar, recent direct measurements may be overestimating its length by 1–1.5 kpc, while its present pattern speed may be 5–10 $\rm km\ s^{-1}\ kpc^{-1}$ smaller than its time-averaged value.
To develop a benchmark measure of US physicians' level of knowledge and extent of use of pharmacogenomic testing, we conducted an anonymous, cross‐sectional, fax‐based, national survey. Of 397,832 ...physicians receiving the survey questionnaire, 10,303 (3%) completed and returned it; the respondents were representative of the overall US physician population. The factors associated with the decision to test were evaluated using χ2 and multivariate logistic regression. Overall, 97.6% of responding physicians agreed that genetic variations may influence drug response, but only 10.3% felt adequately informed about pharmacogenomic testing. Only 12.9% of physicians had ordered a test in the previous 6 months, and 26.4% anticipated ordering a test in the next 6 months. Early and future adopters of testing were more likely to have received training in pharmacogenomics, but only 29.0% of physicians overall had received any education in the field. Our findings highlight the need for more effective physician education on the clinical value, availability, and interpretation of pharmacogenomic tests.
Clinical Pharmacology & Therapeutics (2012); 91 3, 450–458. doi:10.1038/clpt.2011.306
Multiparous cows (n=34, 89 d in milk, 537kg) housed in environmental chambers were fed a control total mixed ration or one containing monensin (450mg/cow per day) during 2 experimental periods (P): ...(1) thermal neutral (TN) conditions (constant 20°C) with ad libitum intake for 9d, and (2) heat stress (HS, n=16) or pair-fed PF; in TN (PFTN); n=18 for 9d. Heat-stress was cyclical with temperatures ranging from 29.4 to 38.9°C. Rectal temperatures and respiration rates increased in HS compared with PFTN cows (38.4 to 40.4°C, 40 to 93 breaths/min). Heat stress reduced dry matter intake (DMI, 28%), and by design, PFTN cows had similar intakes. Monensin-fed cows consumed less DMI (1.59kg/d) independent of environment. Milk yield decreased 29% (9.1kg) in HS and 15% (4.5kg) in PFTN cows, indicating that reduced DMI accounted for only 50% of the decreased milk yield during HS. Monensin had no effect on milk yield in either environment. Both HS and PFTN cows entered into calculated negative energy balance (−2.7 Mcal/d), and feeding monensin increased feed efficiency (7%) regardless of environment. The glucose response to an epinephrine (EPI) challenge increased (27%) during P2 for both HS and PFTN cows, whereas the nonesterified fatty acid response to the EPI challenge was larger (56%) during P2 in the PFTN compared with the HS cows. Compared with P1, whole-body glucose rate of appearance (Ra) decreased similarly during P2 in both HS and PFTN cows (646 vs. 514mmol/h). Although having similar rates of glucose Ra, HS cows synthesized approximately 225g less milk lactose; therefore, on a milk yield basis, glucose Ra decreased (3.3%) in PFTN but increased (5.6%) in HS cows. Regardless of environment, monensin-fed cows had increased (10%) glucose Ra per unit of DMI. From the results we suggest that the liver remains sensitive but adipose tissue becomes refractory to catabolic signals and that glucose Ra (presumably of hepatic origin) is preferentially utilized for processes other than milk synthesis during HS.
•Relation between drag reduction and viscoelasticity of polymers is investigated.•Drag reduction correlates with extensional viscosity and Weissenberg number.•Drag reduction does not correlated with ...small-amplitude oscillatory shear.•For large degradation, extensional viscosity increases with decreasing strain rate.
The relation between the drag reduction (DR) performance of several water-soluble polymers and their viscoelastic properties was investigated. Polymers with a flexible molecular structure including three grades of polyacrylamides (PAM), and a polyethylene oxide (PEO) were investigated. Xanthan gum (XG) and carboxymethyl cellulose (CMC), each with a rigid molecular structure, were also considered. The rheology was characterized using steady shear-viscosity measurement, capillary break-up extensional rheometer (CaBER), and small-amplitude oscillatory shear measurement at the concentration of the drag-reduced solution. To isolate the effect of shear viscosity, the concentration of the polymers was adjusted to produce solutions with a similar shear viscosity at high shear rates. Using pressure drop measurements in a turbulent pipe flow, the DR of each polymer solution was determined. With identical high-shear-rate viscosities, the flexible PAM solutions resulted in an initial DR of 50–58%, while the initial DR of PEO was 44%, and the rigid polymers provided the least DR of 12%. The rigid polymers demonstrated negligible degradation of DR over a period of 2 h. Of the flexible polymers, PAM showed moderate degradation, while the DR of PEO quickly diminished after 20 min. Drag reduction correlated with extensional viscosity and Weissenberg number obtained from CaBER. A strong correlation was not observed between DR and the viscoelastic moduli obtained from small-amplitude oscillatory shear. The large mechanical degradation of PEO was associated with a continuous extensional thickening, in which extensional viscosity increased with decreasing strain rate until the filament broke up.
Summary
Background
Seborrhoeic dermatitis is a chronic relapsing inflammatory skin disease with unclear pathophysiological mechanisms.
Objectives
To establish which lifestyle and physiological ...determinants are associated with seborrhoeic dermatitis.
Methods
Seborrhoeic dermatitis was diagnosed by a trained physician during a full‐body skin examination within the Rotterdam Study, a prospective population‐based cohort study in middle‐aged and elderly people. The current design is a comparative cross‐sectional study embedded in the Rotterdam Study. Potential factors were identified from the literature and analysed in a multivariable logistic regression, including: age, sex, obesity, skin colour, stress, depression, education level, hypertension, climate, xerosis cutis, alcohol and tobacco use.
Results
Of the 5498 participants, 788 participants were diagnosed with seborrhoeic dermatitis (14·3%). We found associations between seborrhoeic dermatitis and male sex adjusted odds ratio (OR) 2·09, 95% confidence interval (CI) 1·77–2·47, darker skin (adjusted OR 0·39, 95% CI 0·22–0·69), season (summer vs. winter: adjusted OR 0·63, 95% CI 0·48–0·82) and generalized xerosis cutis (adjusted OR 1·41, 95% CI 1·11–1·80).
Conclusions
Seborrhoeic dermatitis is one of the most common inflammatory dermatoses in middle‐aged and elderly individuals, especially during winter. Men, and people with a light and dry skin were most likely to have seborrhoeic dermatitis.
What's already known about this topic?
Seborrhoeic dermatitis is a common chronic relapsing inflammatory skin disease with unclear pathophysiological mechanisms.
Numerous host and environmental factors have been implicated in the pathogenesis of seborrhoeic dermatitis, but most have not been validated.
What does this study add?
Male sex, light skin colour, the season winter and generalized dry skin increased the likelihood of having seborrhoeic dermatitis.
Interventions aiming to improve skin‐barrier function could become a target in the treatment of patients with seborrhoeic dermatitis.
Linked Comment: Drucker and Doiron. Br J Dermatol 2018; 178:22–23.
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Preoperative blood pressure (BP) thresholds associated with increased postoperative mortality remain unclear. We investigated the relationship between preoperative BP and 30-day mortality after ...elective non-cardiac surgery.
We performed a cohort study of primary care data from the UK Clinical Practice Research Datalink (2004–13). Parsimonious and fully adjusted multivariable logistic regression models, including restricted cubic splines for numerical systolic and diastolic BP, for 30-day mortality were constructed. The full model included 29 perioperative risk factors, including age, sex, comorbidities, medications, and surgical risk scale. Sensitivity analyses were conducted for age (>65 vs <65 years old) and the timing of BP measurement.
A total of 251 567 adults were included, with 589 (0.23%) deaths within 30 days of surgery. After adjustment for all risk factors, preoperative low BP was consistently associated with statistically significant increases in the odds ratio (OR) of postoperative mortality. Statistically significant risk thresholds started at a preoperative systolic pressure of 119 mm Hg (adjusted OR 1.02 95% confidence interval (CI) 1.01–1.02) compared with the reference (120 mm Hg) and diastolic pressure of 63 mm Hg OR 1.24 (95% CI 1.03–1.49) compared with the reference (80 mm Hg). As BP decreased, the OR of mortality risk increased. Subgroup analysis demonstrated that the risk associated with low BP was confined to the elderly. Adjusted analyses identified that diastolic hypertension was associated with increased postoperative mortality in the whole cohort.
In this large observational study we identified a significant dose-dependent association between low preoperative BP values and increased postoperative mortality in the elderly. In the whole population, elevated diastolic, not systolic, BP was associated with increased mortality.
This paper discusses the presence of steady-state limit cycles in digitally controlled pulse-width modulation (PWM) converters, and suggests conditions on the control law and the quantization ...resolution for their elimination. It then introduces single-phase and multi-phase controlled digital dither as a means of increasing the effective resolution of digital PWM (DPWM) modules, allowing for the use of low resolution DPWM units in high regulation accuracy applications. Bounds on the number of bits of dither that can be used in a particular converter are derived. Finally, experimental results confirming the theoretical analysis are presented.
ABSTRACT
A variety of large-scale diffuse radio structures have been identified in many clusters with the advent of new state-of-the-art facilities in radio astronomy. Among these diffuse radio ...structures, radio mini-halos are found in the central regions of cool core clusters. Their origin is still unknown and they are challenging to discover; less than 30 have been published to date. Based on new VLA observations, we confirmed the mini-halo in the massive strong cool core cluster PKS 0745−191 (z = 0.1028) and discovered one in the massive cool core cluster MACS J1447.4+0827 (z = 0.3755). Furthermore, using a detailed analysis of all known mini-halos, we explore the relation between mini-halos and active galactic nucleus (AGN) feedback processes from the central galaxy. We find evidence of strong, previously unknown correlations between mini-halo radio power and X-ray cavity power, and between mini-halo and the central galaxy radio power related to the relativistic jets when spectrally decomposing the AGN radio emission into a component for past outbursts and one for ongoing accretion. Overall, our study indicates that mini-halos are directly connected to the central AGN in clusters, following previous suppositions. We hypothesize that AGN feedback may be one of the dominant mechanisms giving rise to mini-halos by injecting energy into the intra-cluster medium and reaccelerating an old population of particles, while sloshing motion may drive the overall shape of mini-halos inside cold fronts. AGN feedback may therefore not only play a vital role in offsetting cooling in cool core clusters, but may also play a fundamental role in re-energizing non-thermal particles in clusters.
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